It's no wonder health myths abound. For example, as a kid you may have believed that if you didn't wait an hour after eating to go swimming, you'd get a stomach cramp and drown. Not true—unless you've eaten lead. But sometimes what sounds like a myth may be true. For example, wearing briefs that are too tight can indeed lower your sperm count.

Myth: Men Don't Get Osteoporosis

Fact: While women are four times more likely to develop osteoporosis than men, one out of eight men over the age of 50 is at risk. It's a sneaky disease because many people don't realize they're losing bone density until a brittle bone fractures. Proportionally, more men than women who have the disease suffer hip fractures, and men are twice as likely as women to die within a year after breaking a hip.

The National Osteoporosis Foundation (NOF) says osteoporosis in men is under-diagnosed, under-reported, and inadequately researched. What is known is that age, certain medical conditions (eg cancer and some of its treatments), medications, and bad habits speed bone loss. The NOF advocates a diet rich in ]]>calcium]]> and ]]>vitamin D]]> . They caution against smoking and excessive use of alcohol . And they have launched the Step On It America! campaign to promote weight-bearing exercise, such as ]]>walking]]> , dancing, playing ]]>tennis]]> , and ]]>strength training]]> .

Myth: Shaving Your Head Will Make Hair Grow Back Thicker

Fact: Don't bother. But the good news about this myth is that it doesn't cost anything. You could spend a fortune chasing other so-called ]]>hair-loss]]> remedies that don't work either: special shampoos, creams, scalp massage, electrical stimulation, and vitamins.

Many prescription and nonprescription treatments are available. But the American Academy of Dermatology cautions consumers to be wary of drugs and herbal remedies that aren't approved by the FDA for treating hair loss. So far the oral drug finasteride (Proscar) and topical drug minoxidil (Rogaine) are the only two products that have passed FDA trials.

Myth: Depression Is a Sign of Personal Weakness

Fact: Major depression is not a sign of personal weakness. "It's a bona fide disorder with characteristic symptoms: insomnia, particularly waking up at 3:00 or 4:00 a.m., poor appetite, weight loss, low energy, loss of interest in usual activities, and oftentimes thoughts of suicide," says Steven Wengel, MD, associate professor of psychiatry at the University of Nebraska Medical Center. "There are tests done in a research setting that demonstrate there really are brain changes with depression. One thing we know is that certain brain receptors are altered either in number or sensitivity, and that the brain changes back to normal after a patient has been successfully treated."

Men are less likely to seek help than women and are four times more likely to commit suicide.

"The data suggests that women have about twice the lifetime frequency of major depression, but it makes you wonder if the numbers could be biased due to men being more reluctant to get help," says Dr. Wengel. "It's unfortunate because depression is not only a common disease, it's also one of the most treatable."

Myth: Having the Mumps as a Child Will Make You Sterile

Fact: Having mumps as a child probably gave you just a sore, swollen neck for a few days. But there is a 25% risk of becoming sterile if you get the disease after puberty.

"When kids get the mumps, it's usually pretty benign," says Thomas Brady, MD. Dr. Brady is in private practice in Reno, Nevada, and a clinical professor of urology at the University of Nevada. He says the disease is a virus that can spread from the neck's parotid gland to other organs. "When a man gets mumps, he can be sick for a long time, and the disease can 'go down.' The testicle can shrivel up to the size of a pea."

Myth: Having a Vasectomy Will Increase Your Risk of Heart Disease

Fact: "The real facts appear to be that there's no connection between ]]>vasectomy]]> and any disease process over and above being sterile," says Dr. Brady. "At various times I've seen it linked to heart disease, prostate cancer, multiple sclerosis and obesity, but there's no connection."

According to literature published by the National Institute of Child Health and Human Development (NICHD), the concern about heart disease was raised in the late 1970s, but numerous studies since then have found no connection to vasectomy. Similarly, a reported link between vasectomy and prostate cancer has generated a tremendous amount of attention. Extensive reviews and investigation by NICHD and the World Health Organization (WHO) have found no physiological reason that vasectomy could cause cancer and suggest that earlier studies reporting a link may have been flawed.

A large study called the "Health Status of American Men" was conducted by the NICHD and involved questioning more than 10,000 males eight to 10 years after vasectomy and an equal number who had not been vasectomized. The study looked at 99 different disorders and found only one to be more common after vasectomy: inflammation of the testicles occurred in some in the year following surgery. The condition usually goes away after a week of heat treatments.

Myth: Loss of Muscle Mass Is Inevitable With Old Age

Fact: It's the combination of inactivity with aging that causes muscles to shrivel. "If you take a 50-year-old man who's exercised properly all his life, he'll have the body of a 30- year-old," says Edward Jackowski, PhD, CEO of Exude Inc. "Take a 30-year-old who's been a sloth, and he'll have the body of a 70-year-old."

"A number of studies prove that you can build muscle mass at any age," Dr. Jackowski explains. "It's only when you're inactive that, synergistically as you become older, you lose muscle faster."

Myth: Viagra Can Boost the Sexual Prowess of a Normally Potent Man

Fact: Viagra helps men who have erectile dysfunction—men who can't complete the sex act to their satisfaction because they're unable to achieve or sustain an erection. It's not an aphrodisiac, it won't prevent premature ejaculation , and it won't make a 45-year-old 18 again.

Dr. Brady says when a normally functional man asks for Viagra, he sits him down and talks about becoming comfortable with his sexuality. "I'm not trying to make them young stallions," says Dr. Brady. "I had one man come in here saying he was having sex twice a day, and that wasn't enough! You have to have realistic expectations."